Impact of climate change on environmental niche dynamics of resident and migratory ducks in the Eastern Himalayan wintering grounds

Climate change is profoundly reshaping the distribution and interspecific dynamics of waterbirds across wintering grounds worldwide, yet its implications for niche overlap between migratory and resident guilds remain poorly assessed, particularly in biodiversity-rich South Asian landscapes. This study quantified habitat suitability and niche overlap between two abundant migratory duck species ( Anas acuta and Mareca strepera ) and two resident duck species ( Dendrocygna javanica , and Anas poecilorhyncha ) across the eastern Himalayan wintering grounds of Assam, under current and projected future climatic conditions. Using a multi-algorithm ensemble species distribution model integrating MaxEnt, Random Forest, GLM and SVM, calibrated with eight non-collinear environmental predictors, we generated habitat suitability maps under two Shared Socioeconomic Pathways (SSP245 and SSP585) for mid-future (2041–2060) using the HadGEM3-GC31-LL and IPSL-CM6A-LR (CMIP6) climate model. The ensemble model performed robustly for both guilds (AUC: 0.84–0.85; TSS: 0.57). the Euclidean distance from river appeared as the most influential variable for both groups (32.5%). Under current conditions, the two guilds exhibited high niche overlap, with a spatial overlap area of 11,160.36 km 2 . These findings suggest the two guilds are not only co-distributed but are largely co-occurring across the same habitat patches within the Brahmaputra floodplain, indicating high shared area for space and resources